Re: When a test is too good: how CT pulmonary angiograms find pulmonary emboli that do not need to be found
Weiner and colleagues(1) have opened this journal’s ‘too much medicine’ series with an excellent article that provokes thought and challenges current practice.
They have highlighted the uncertainty that exists with subsegmental pulmonary embolism that includes its diagnosis and management. They describe the harm that may come to patients from both the radiation exposure of CT pulmonary angiography as an investigation, and from anti-coagulation as treatment. The evidence they present, despite its limitations, supports the notion that this condition is overdiagnosed and overtreated.
However, we suggest that the advice on how to address this problem, would be difficult to follow for the majority of in-patients, and in particular, surgical patients.
In the UK, both the British Thoracic Society guidelines(2), and their successor, published by the National Institute for Clinical Excellence(3), recommend CT pulmonary angiogram (CTPA) as first line investigation for those rated as ‘likely’ on the Wells criteria. Those rated ‘unlikely’ are to be investigated with a D-dimer test, which, if positive, would then require CTPA.
According to NICE the VQ scan is to be offered to those with renal impairment, allergy to contrast media, or to those to whom the risk of irradiation is unacceptable.
Given these guidelines, it would seem difficult to reduce the number of medical and surgical inpatients suspected of having a pulmonary embolism, from receiving CTPA as investigation. Surgical patients will either be rated as ‘likely’, or will provide a D-dimer test that is considered difficult or impossible to interpret(4, 5)In addition, the reliability of clinical prediction rules for pulmonary embolism may decrease when applied to inpatients and trauma patients(6, 7). The proposed reduction in CTPA use therefore, would depend on the proportion of investigations that are provided on an outpatient or inpatient basis.
The alternative to treating all clinically stable patients with subsegmental pulmonary emboli with anti-coagulants is described as continued monitoring with serial ultrasonography. This seems a reasonable suggestion, however it would place an extra logistical burden on radiology departments, and require further compliance and attendance from patients.
Evidence guiding which pulmonary emboli can safely be left untreated would have significant value, both to the patient and the healthcare institution. The authors state those questions we need to answer with regard to the prognosis and outcomes of untreated subsegmental pulmonary emboli. We would also be interested to know if these outcomes differ for different patient groups, such as surgical, medical, inpatient or outpatient.
Whilst we congratulate the authors on highlighting this issue, we feel there is a great amount of work still to be done before a significant change in practice is seen. We look forward to seeing the results of the prospective cohort study they reference.
1. Wiener RS, Schwartz LM, Woloshin S. When a test is too good: how CT pulmonary angiograms find pulmonary emboli that do not need to be found. BMJ. 2013;347:f3368.
2. British Thoracic Society Standards of Care Committee Pulmonary Embolism Guideline Development Group. British Thoracic Society guidelines for the management of suspected acute pulmonary embolism. Thorax. 2003;58(6):470-83.
3. Langford N, Stansby G, Avital L. The management of venous thromboembolic diseases and the role of thrombophilia testing: summary of NICE Guideline CG144. Acute medicine. 2012;11(3):138-42.
4. Dindo D, Breitenstein S, Hahnloser D, Seifert B, Yakarisik S, Asmis LM, et al. Kinetics of D-dimer after general surgery. Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis. 2009;20(5):347-52.
5. Lippi G, Veraldi GF, Fraccaroli M, Manzato F, Cordiano C, Guidi G. Variation of plasma D-dimer following surgery: implications for prediction of postoperative venous thromboembolism. Clinical and experimental medicine. 2001;1(3):161-4.
6. Ollenberger GP, Worsley DF. Effect of patient location on the performance of clinical models to predict pulmonary embolism. Thrombosis research. 2006;118(6):685-90.
7. Young MD, Daniels AH, Evangelista PT, Reinert SE, Ritterman S, Christino MA, et al. Predicting pulmonary embolus in orthopedic trauma patients using the Wells score. Orthopedics. 2013;36(5):e642-7.
Rapid Response:
Re: When a test is too good: how CT pulmonary angiograms find pulmonary emboli that do not need to be found
Weiner and colleagues(1) have opened this journal’s ‘too much medicine’ series with an excellent article that provokes thought and challenges current practice.
They have highlighted the uncertainty that exists with subsegmental pulmonary embolism that includes its diagnosis and management. They describe the harm that may come to patients from both the radiation exposure of CT pulmonary angiography as an investigation, and from anti-coagulation as treatment. The evidence they present, despite its limitations, supports the notion that this condition is overdiagnosed and overtreated.
However, we suggest that the advice on how to address this problem, would be difficult to follow for the majority of in-patients, and in particular, surgical patients.
In the UK, both the British Thoracic Society guidelines(2), and their successor, published by the National Institute for Clinical Excellence(3), recommend CT pulmonary angiogram (CTPA) as first line investigation for those rated as ‘likely’ on the Wells criteria. Those rated ‘unlikely’ are to be investigated with a D-dimer test, which, if positive, would then require CTPA.
According to NICE the VQ scan is to be offered to those with renal impairment, allergy to contrast media, or to those to whom the risk of irradiation is unacceptable.
Given these guidelines, it would seem difficult to reduce the number of medical and surgical inpatients suspected of having a pulmonary embolism, from receiving CTPA as investigation. Surgical patients will either be rated as ‘likely’, or will provide a D-dimer test that is considered difficult or impossible to interpret(4, 5)In addition, the reliability of clinical prediction rules for pulmonary embolism may decrease when applied to inpatients and trauma patients(6, 7). The proposed reduction in CTPA use therefore, would depend on the proportion of investigations that are provided on an outpatient or inpatient basis.
The alternative to treating all clinically stable patients with subsegmental pulmonary emboli with anti-coagulants is described as continued monitoring with serial ultrasonography. This seems a reasonable suggestion, however it would place an extra logistical burden on radiology departments, and require further compliance and attendance from patients.
Evidence guiding which pulmonary emboli can safely be left untreated would have significant value, both to the patient and the healthcare institution. The authors state those questions we need to answer with regard to the prognosis and outcomes of untreated subsegmental pulmonary emboli. We would also be interested to know if these outcomes differ for different patient groups, such as surgical, medical, inpatient or outpatient.
Whilst we congratulate the authors on highlighting this issue, we feel there is a great amount of work still to be done before a significant change in practice is seen. We look forward to seeing the results of the prospective cohort study they reference.
1. Wiener RS, Schwartz LM, Woloshin S. When a test is too good: how CT pulmonary angiograms find pulmonary emboli that do not need to be found. BMJ. 2013;347:f3368.
2. British Thoracic Society Standards of Care Committee Pulmonary Embolism Guideline Development Group. British Thoracic Society guidelines for the management of suspected acute pulmonary embolism. Thorax. 2003;58(6):470-83.
3. Langford N, Stansby G, Avital L. The management of venous thromboembolic diseases and the role of thrombophilia testing: summary of NICE Guideline CG144. Acute medicine. 2012;11(3):138-42.
4. Dindo D, Breitenstein S, Hahnloser D, Seifert B, Yakarisik S, Asmis LM, et al. Kinetics of D-dimer after general surgery. Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis. 2009;20(5):347-52.
5. Lippi G, Veraldi GF, Fraccaroli M, Manzato F, Cordiano C, Guidi G. Variation of plasma D-dimer following surgery: implications for prediction of postoperative venous thromboembolism. Clinical and experimental medicine. 2001;1(3):161-4.
6. Ollenberger GP, Worsley DF. Effect of patient location on the performance of clinical models to predict pulmonary embolism. Thrombosis research. 2006;118(6):685-90.
7. Young MD, Daniels AH, Evangelista PT, Reinert SE, Ritterman S, Christino MA, et al. Predicting pulmonary embolus in orthopedic trauma patients using the Wells score. Orthopedics. 2013;36(5):e642-7.
Competing interests: No competing interests